Wavelength division multiplexed (WDM) transmission systems currently use integrated optical arrayed waveguide routers (AWRs) to multiplex individual wavelength signals onto a single fiber and to demultiplex the signals received over a fiber. However, as the number of channels used in WDM transmission systems increases, suitable AWRs become increasingly difficult to design and fabricate. Some of the difficulties involved are forming flat passbands, and suppressing the interchannel crosstalk from the many output lines. Using today's technology, it should be possible to manufacture an 128 channel router with a 50 GHz spacing, but further increases to the channel count will probably require a new approach.
What is desired is a technique for increasing the number of channels that can be used in WDM transmission systems.